Many important advances in cellular and molecular biology are attributable to structure-function analysis of proteins that .govern function in individual cells or populations of cells. Solid phase peptide synthesis (SPPS) of small peptides, or defined structural, functional, or immunogenic domains of larger proteins, has enabled characterization of structure-activity relationships (SAR) within these molecules that could not be achieved otherwise. The increasing reliance on peptide synthesis by an array of investigators at the Harbor-UCLA Research and Education Institute is the basis for the current effort to acquire a combinatorial SPPS instrument, to expand and modernize the capabilities of the Biopolymer Synthesis Core Facility at Harbor-UCLA REI. As an integral component of this Core Facility, the proposed instrument is adaptable to a wide diversity of peptide syntheses. Thus, peptides produced by this instrument will serve as excellent reagents for a broad array of biomedical research projects. For example, such peptides are invaluable for conducting SAR studies, examining peptide- target cell interactions by flow cytometry, and localization of peptides in situ. Likewise, SPPS enables the production of peptides containing unusual alkylated, alpha,beta-dehydro, and D-enantiomer amino acids crucial for studying conformation as it relates to peptide or protein function. Contemporary expression systems and site-directed mutagenesis approaches are not feasible for routine and rapid production of such peptides. The combinatorial synthesis capability of the proposed instrument will enhance the efficiency of our Core Facility by enabling simultaneous synthesis of multiple, distinct peptides. Applications for unlabeled or labeled peptide reagents to be generated by the proposed instrument for use in NIH-sponsored projects include: 1) protein or peptide functional domain scanning; 2) evaluation of key SAR within proteins and peptides using non-radioactive 13 C- and 15-N-peptide libraries and FTIR or NMR spectroscopy; 3) screening of expression libraries or mutant clones probed with labeled or unlabeled peptides; 4) design and synthesis of peptides with antimicrobial, antitumor, or immunopotentiating properties for eventual therapeutic evaluation; and 5) synthesis of antigen or diagnostic peptide reagents to detect or characterize immunogen targets for vaccine development. Operation and management of the instrument will be streamlined using a simple algorithm coordinating the entire process from on-line peptide synthesis request, to delivery of quality-controlled peptides to investigators, to recharge accounting. The Harbor-UCLA REI is maximally supportive of the long-term success of the instrument as part of the Biopolymer Synthesis Core Facility. Therefore, the proposed instrument will significantly enhance the efficiency and diversity of SPPS required for NIH-sponsored and hypothesis-driven research.